Difference between revisions of "ETRA SOM/ETRA Hardware/Power and Reset/Power Supply Unit (PSU) and recommended power-up sequence"

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== Power Supply Unit (PSU) and recommended power-up sequence ==
 
== Power Supply Unit (PSU) and recommended power-up sequence ==
Implementing correct power-up sequence for ''TBD: SOC ''' processors is not a trivial task because several power rails are involved.  
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Implementing correct power-up sequence for ''STM32MP1'' processors is not a trivial task because several power rails are involved.  
  
ETRA SOM simplifies this task by embedding all the needed circuitry. The following picture shows a simplified block diagram of PSU/voltage monitoring circuitry:
+
ETRA SOM includes a PMIC that manage all the power on and poweroff timings to ensure the correct sequence
 +
 
 +
The following picture shows a simplified block diagram of PSU circuitry:
  
 
[[File:ETRA-power-sequence.png | 800px]]
 
[[File:ETRA-power-sequence.png | 800px]]
 
The PSU is composed of two main blocks:
 
* power management integrated circuit
 
* additional generic power management circuitry that completes PMIC functionalities
 
  
 
The PSU:
 
The PSU:
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''TBD: descrizione dei segnali che intervengono nella PS''
 
''TBD: descrizione dei segnali che intervengono nella PS''
  
==== Note on BOARD_PGOOD usage ====
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==== Note on SOM_PGOOD usage ====
 
 
''TBD: verificare le note sul BOARD_PGOOD''
 
 
 
BOARD_PGOOD is generally used on carrier board to drive loads such as DC/DC enable inputs or switch on/off control signals.
 
 
 
Depending on the kind of such loads, BOARD_PGOOD might not be able to drive them properly. In these cases a simple 2-input AND port can be used to address this issue. The following picture depicts a principle schematic showing this solution.
 
 
 
VDD_SOM denotes the power rail used to power ETRA SoM.
 
 
 
[[File:ETRA-power-good.png]]
 
  
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SOM_PGOOD is generally used on carrier board to drive loads such as DC/DC enable inputs or switch on/off control signals.
  
 +
Depending on the kind of such loads, SOM_PGOOD might not be able to drive them properly. On ETRA SOM this signal is driven by the VDD rail so, if many loads has to be driven, connect them to the VDD output pins through a resistor.
 
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[[Category:ETRA]]
 
[[Category:ETRA]]

Revision as of 15:19, 29 December 2020

History
Version Issue Date Notes
0.9.0 Dec 2020 First Draft
[TBD_link X.Y.Z] Month Year TBD
... ... ...


Power Supply Unit (PSU) and recommended power-up sequence[edit | edit source]

Implementing correct power-up sequence for STM32MP1 processors is not a trivial task because several power rails are involved.

ETRA SOM includes a PMIC that manage all the power on and poweroff timings to ensure the correct sequence

The following picture shows a simplified block diagram of PSU circuitry:

ETRA-power-sequence.png

The PSU:

  • generates the proper power-up sequence required by the SOC processor and surrounding memories and peripherals
  • synchronizes the powering up of carrier board in order to prevent back power
  • provides some spare regulated voltages that can be used to power carrier board devices

Power-up sequence[edit | edit source]

TBD: descrizione dei segnali che intervengono nella PS

Note on SOM_PGOOD usage[edit | edit source]

SOM_PGOOD is generally used on carrier board to drive loads such as DC/DC enable inputs or switch on/off control signals.

Depending on the kind of such loads, SOM_PGOOD might not be able to drive them properly. On ETRA SOM this signal is driven by the VDD rail so, if many loads has to be driven, connect them to the VDD output pins through a resistor.